PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) from the atmosphere of Xi'an, China: Seasonal variation, sources, and health risk assessments

Abstract

Ambient air samples of fine particulate matter (PM_2.5) were collected in a main urban area of Xi'an, Guanzhong Plain, whose contents including organic carbon (OC), elemental carbon (EC) and eight carbon components were measured by thermo-optical analysis. Polycyclic aromatic hydrocarbons (PAHs) were determined by high-performance liquid chromatography. As a result, OC and EC accounted for 74.5% of PM_2.5 in winter. During winter, light-molecular-weight PAHs (with 2 and 3 benzene rings) concentration predominated in the atmosphere. Molecular diagnostic ratios were calculated to distinguish between different sources of carbon components and PAHs, which revealed natural dust, fossil fuels combustion, and traffic emissions (diesel and gasoline emissions) were the major source contributors. Health risk assessment of PAHs indicated the non-carcinogenic risk values were far lower than 1 for all populations. Some carcinogenic risk values induced by PM_2.5-bound PAHs were higher than 10⁻⁶, which means that there was a certain potential carcinogenic risk in carcinogenic PAHs. High exposure pollutants (acenaphthylene, benzo(b) fluoranthene, naphthalene and chrysene) were observed with potential in vitro oxidative and inflammatory responses. The results showed that long-term exposure to the environment with PAHs pollutants could cause sustained immune and respiratory system damage to the human body. Air quality management should be carried out to improve ambient air quality and reduce health hazards.